What is the purpose of supplying the AC to rectifier through capacitors

[Mark Johnson]

If your digital voltmeter's input impedance is 1 Megohm or more {as 99% of them are}, you can simply measure the DC voltage across each electrolytic capacitor. Connect the "+" terminal of the DVM to the "+" terminal of the electrolytic capacitor, and connect the "-" terminal of the DVM to the "-" terminal of the electrolytic capacitor. Let the circuit stabilize for 30 seconds after power-on, and them measure & write down the voltages. There are only six electrolytic caps on the schematic of post #1, helpfully labeled C1 - C6, so this won't take much time at all.

Now check to see whether your measured voltage across electrolytic capacitor C1 is polarized according to the schematic. Repeat for C2 thru C6. Voila you now possess the right answer, and you don't have to trust anybody else's opinion and you don't have to run a circuit simulation program.

 

[Bas Horneman]

Thanks Mark! Teaching a man how to fish instead of giving him fish! I'll try it this evening.

 

[Bas Horneman]

PS the designer uses non-polarized caps now.

 

[Bas Horneman]

Relative to common ground:
C1,C3 = 12 VDC
C3,4 = 8.2 VDC
C5 = 16 VDC
C6 = 15 VDC

Negative probe on - of c1 and red probe on + of c1 I measure -8 VDC.
Same for c2.

 

[Bas Horneman]

Reversed c1 and c2. All measurements to common ground are the same as above.

Measuring the caps as per polarity. Shows 8V now!

Thanks Ed, Mark and Erik!
ps. I used 120uF caps. No difference in voltage compared to the 47uF.

 

[Bas Horneman]

PS. This circuit can take a hit! I tested on a board that was not in my preamp. And I accidentally tested with 12,6V ac on the board....(all voltages above were *2 and it survived). Heatsink blistering hot. With 6,3vac in and one el84 connected it runs pretty cool.

 

[Bas Horneman]

These are the ones in my preamp. Took the board out to change polarity. Put in new caps. Clearly bulging. So I was talking **** about them not bulging.

 

[Bas Horneman]

Back to my question about it being a highish impedance supply....

Anyone care to educate me?

 

[v4lve lover]

This is a low impedance supply for preamp tubes. It works up to 2.5-3A .

You are right, i messed up the polarity of the caps. Last 30 modules used uvp 25V bipolar caps.

Its very nice for heating 6v6 and the likes

 

[Bas Horneman]

Thanks v4lve lover. That is exactly what I use it for. My Salas 6V6 preamp. Well I'm not right. The folks who do this for a living told me.
Ok...since it is a low impedance supply I'll keep using it for heaters but will use tentlabs and coleman regs for filaments.

 

[Nico Ras]

Simple, it makes it AC and prevents any DC offset sitting on your mains. It is something we have done for years ensuring thatr there is no DC magentising the transformer core. All the crap half wave rectified dimmers, hair dryers causes mains to become offset.

 

[Bas Horneman]

Check again. This is not in front of a transformer.
To save you from reading here is the answer in my thread: https://www.diyaudio.com/community/...tifier-through-capacitors.410214/post-7625201

 

[Nico Ras]

Good grief, you are smart. Maybe I should have looked at the schematic. Pretty stupid. Left my reading glasses somewhere I could not find it. They where on my wheelchair.

 

[Bas Horneman]

I would not say I'm smart. Not stupid either. More of a smartass.